不同金属对硼球烯的修饰作用

系统研究了3类金属,包括碱金属(M=Li、Na、K)、碱土金属(M=Be、Mg、Ca)及部分过渡金属(M=Ni、Pd、Pt、Cu、Ag、Au)修饰的B40的结构与稳定性,发现除Na和Ca是内嵌结构稳定以外,其余金属原子都倾向于形成外挂结构.随着金属原子数目的增多,Li,Na,K,Ag的平均结合能变化不大;而Be、Mg、Ca、Ni、Pd、Cu则与B40腰上的4个七元环作用能量上更有利,故当原子数目大于4时,平均结合能有所升高.Pt的原子数目升高到6时,B40笼子的主体已经严重变形.此外,随着金属原子数目增多,Ag原子有可能会团聚成金属团簇,Au不仅会形成小的Au团簇,还会改变B40的主体结构,从而形成更复杂的相结构.Bader电荷分析表明,碱金属和碱土金属与B40笼子的离子作用更强,而过渡金属原子则主要以共价作用或配位作用与B40相结合.该研究结果表明Ni有可能是稳定B40笼子的较好选择,其次是Pd.Ni、Pd的掺杂有可能帮助实验实现这一特殊硼球烯结构的制备.

Decoration of borospherene B40 by different metals

Decoration of borospherene B40 by different metals,including three types of metals: alkali metal(M =Li,Na,K),alkaline earth metal(M = Be,Mg,Ca) and some transition metals(M = Ni,Pd,Pt,Cu,Ag,Au),have been systemically studied. It is found that endohedral M@ B40(M = Na,Ca) with a metal atom at the center is more stable than the exohedral borospherene structures,while exohedral M&B40 for other metals is more favored than the endohedral geometries. With the increase of the number of metal atoms,the average binding energies of Li,Na,K and Ag have little change. However,for Be,Mg,Ca,Ni,Pd and Cu,the metal atom face-capping a heptagon on the B40 waist is more favored than that of a hexagon; therefore when the number of metal atoms is over 4,the average binding energy has increased. The structure of the B40 cage has been severely deformed when the number of Pt atoms increases to 6. In addition,as the number of metal atoms increases,Ag atoms may agglomerate into metal clusters; Au will not only form small Au clusters,but also change the cage structure of B40 to form more complex phases. The Bader charge analysis shows that the alkali metal and alkaline earth metals have a strong ion effect interacting with B40,while the transition metal atoms mainly bind to B40 through some covalent or coordination effect. It shows that the decoration with Ni or Pd may stabilize the B40 cage structure and help the experimental preparation of this special cage.